Effects on the Neural Tube and Its Derivatives

Exencephaly and associated eye defects were edso observed in rat embryos surviving culture in vitro for 48 h on serum from cadmium-treated rats. Since the embryos were explanted at head-fold stage, the culture test period overlapped with the gestational ages challenged in the in utero studies reported by Barr. Exencephaly was not seen in the in utero studies, but eye 

Tsujii and Hoshishima have performed a comprehensive series of behavioral tests in order to monitor development of reflex responses in mice bom to mothers that received 11 daily intraperitoneal injections (10 ng/mouse) during gestation (3 consecutive days followed by 8 alternate days). These authors concluded that cadmium treatment influenced development of reflex responses, either accelerating or retarding the process depending on the specific test administered. Tsujii and Hoshishima also re- 

Webster and Messerle reported that in the C57BL/6J strain used in their studies, the neural tube was closed in embryos collected on gestation day 9 except at the anterior and posterior neuropore. The neurcil tube of control embryos collected on gestation day 10 was completely closed. In embryos collected on gestation day 10, following treatment on either gestation day 7 or 8, the 

Plausible hypotheses to explain cadmium interference with neural tube closure may be developed on the basis of the importance of cell surface modifications and/or microfllaments and microtubules in the neurulation process, although observations bearing directly on these possibilities have yet to be reported. Virtual restriction of cadmium interference with neural tube closure to the cephalic region, however, would require additional assumptions. This suggests the likelihood that cadmium is affecting some aspect of the closure process that is either peculiar to, or of overriding importance for, closure of the cephalic neural tube. 

The identity of the gene loci influencing the teratogenic response to cadmium has yet to be determined. At the present time any simple relationship between teratogenicity and a lo- 

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